Freeness testing apparatus and method



J1me 1965 D. w. DANFORTH 3,

FREENESS TESTING APPARATUS AND METHOD Filed March 6, 1961 LIQUID LEVEL RECORDER 2 Sheets-Sheet l VACUUM OR ATMOSPHERE JNVENTOR.

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v-Peaamu ATTQRNEYS' June 1, 1965 Filed Mai-ch 6, 1961 D. W. DANFORTH FREENESS TESTING APPARATUS AND METHOD 2 Sheets-Sheet 2 Fig.6.-

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I A TTQRNEM" United States Patent 3,186,215 FREENESS TEfiTiNG APPARATUL, AND METHOD Donald W. Danforth, Andover, Mass, assignor to John W. Bolton 8; Sons, Inc., Lawrence, Mass, a corporation of Massachusetts Filed ii tar. 6, 195:1, Ser. No. 93,593 1'7 tfiiaims. (CI. 7363) This invention relates to an apparatus and method for continuously and automatically testing the freeness of paper stock while the stock is flowing in a closed system toward the paper making machine. It also relates to a novel control for the refiners of such a system wherein variations in uniformity of stock are sensed in advance of the paper making machine by periodic freeness tests which automatically compensate for such variations by regulating the refiners.

In the paper making art free stock is that which consists of coarse fibres which drain quickly and will not readily felt when squeezed. Slow stock is that which consists of fine fibers, with frayed ends, from which a dense mat is formed from which water drains slowly. The degree of freeness of paper stock is determined by the rate of drainage of water from it, under a given set of conditions. Other factors being equal, the freeness is an indication of the amount of refining done on a stock.

In order to maintain the properties of paper at a constant level, it is desirable to closely control the action of equipment which affects these properties, especially the refiners such as the Iordans, Claflins and disc refiners. It is possible to control the action of these refiners by methods which keep the action of the refiner constant or by methods which regulate the action of the refiners to keep the results, or properties of the stock constant.

The latter method of regulating the refiners to compensate for variations in stock properties has heretofore een attempted, for example, by determining the freeness of the stock by measuring the vacuum at the couch roll of the Fourdrinier machine. The paper stock has, of course, already been deposited on the wire in this zone and it is too late to make corrections in the properties of such deposited paper. It has also been proposed to regulate the refiners by determining freeness of the stock in advance of the paper making machine, in the stock preparation zone, by continuously sampling stock diverted into a by-pass from the closed stock lines, such sampling machines usually constituting a small scale Fourdrinier with a traveling meshed belt or rotating meshed drum. As far as I am aware, there has been no apparatus in the prior art for automatically testing freeness of stock as the stock flows in the closed pipe line system from the refiners and while the stock remains in the system, the apparatus immediately regulating the refiners to correct variations of properties of the stock before the paper is formed. Consistency of the stock, temperature, the nature of the fibres and other stock properties can usually be maintained reasonably constant. If freeness of the stock arriving at the paper making machine is also maintained constant, the uniformity of the properties of the resulting paper product is virtually assured.

It is the object of this invention, therefore, to provide an apparatus mounted directly on a closed paper stock line in the stock preparation zone for continuously testing the freeness of stock in the line and visually indicating the results of each successive test to an operator.

Another object of the invention is to provide apparatus for continuously and automatically determining the freeness of stock flowing through a closed paper stock line, automatically recording the freeness determined 3,186,215 i atented June 1, 1965 ice and automatically regulating the refiners to compensate for any variations from the normal, or predetermined, freeness.

A further object of the invention is to provide a simple, rugged, freeness detector having no moving parts and mounted directly on a main stock line in the stock preparation area of a closed paper stock system in rear of the refiners but in advance of the paper making machine. The automatic actuation of the detector at preselected time intervals permits an operator to note any variations from the desired, uniform, freeness and to correct the same by regulation of the refiners.

Still another object of the invention is to provide a method of automatically maintaining uniformity of paper stock -by periodic tests of freeness in stock flowing through a closed stock line and immediate correction of any variations in freeness by automatic regulation of the refiners feeding stock to the line.

A still further object of the invention is to provide improved freeness testing apparatus which has no moving parts, is totally enclosed, self cleaning and provides a visual indication of freeness, at any time interval desired, of stock flowing in a closed paper stock line.

Other objects and advantages of the invention will be apparent from the claims, the description of the drawings and from the drawings in which FIG. 1 is a side elevation of freeness tester apparatus constructed in accordance with the invention and mounted on a main paper stock line,

FIGS. 25 are fragmentary views, similar to FIGURE 1 showing the cycle of operation of the freeness tester,

FIG. 6 is a View similar to FIG. 1, on a reduced scale, showing a fully automatic paper stock system with the refiners regulated by the results of automatic, continuous freeness testing on the closed stock line supplied by the refiners and leading toward the paper making machine. The paper making machine and refiners are shown diagrammatically on a greatly reduced scale.

As best shown in FIG. 6 a typical paper stock prepa ration zone 20 includes equipment for providing paper pulp with such properties as are desired in the resulting paper, for example, Jordan refiners such as 21. The refiner, or refiners, 21 usually include automatic controls for positioning the refiner plugs or discs, or controlling the pressure on the plugs or discs, typified by the pneumatic actuator 22 for moving the refiner rotor axially with relation to the stator. Such automatic controls, whether pneumatic or electric, are well known in the trade and, therefore, not described in detail herein. The refiner, or refiners, 21 delivers refined stock into a closed paper stock line 23 which may lead to other processing equipment, to stock chests or the like, but which eventually directs the stock into the head box 24 of a paper making machine such as the Fourdrinier 25 in the paper making zone 26. In one well known type of pneumatic refiner control, the actuator 22 includes a diaphragm 19 with an air pressure supply line 27 leading to one side thereof and another air pressure supply line 28 leading to the opposite side thereof for advancing and retracting the plug to increase or decrease the refining action on the stock 29. The diaphragm 19 is mounted on the shaft 18 of the refiner plug 17, the shaft being carried in slidable bearings 16 connected by flexible coupling 15 to the drive motor 14. The plug 17 rotates within the truncated conical shell, or stator, 12, the shell having a stock inlet 11 at the small end and a stock outlet 10 at the large end connected to the closed paper stock line 23.

As stated above, it has long been customary to measure the vacuum at a couch, or suction, roll 31 of the Fourdrinier 25 to determine freeness of the paper stock at that location and to regulate the refiners accordingly. In the stock preparation zone 20, however, freeness has 3 usually been determined manually by withdrawing a sample and testing the sample in a laboratory tester or by diverting a stream of the stock away from the closed paper stock system into an open system having a small scale paper making machine therein for determining freeness.

The freeness testing apparatus 32 of this invention is located in some portion of a paper stock system in rear of the refiners 21 and in advance of the paper making machine 25 and preferably on a main paper stock line such as 23, being supplied by the refiners 21 in the stock preparation Zone 20. The apparatus 32 includes the freeness tester, or detector, 33 comprising the vertical standpipe 34 of predetermined height and diameter having a vertical chamber 35 therewithin. Preferably, the standpipe 34 is a cylindrical tube of transparent plastic material having a closed upper end 36 and an open lower end 37. The lower end 37 is enlarged to form a recess 38 for accommodating any one of a plurality of replaceable rings 39, each ring supporting a mat-forming screen 41 thereacross of various predetermined mesh sizes. When the standpipe is mounted vertically, the screen 41 extends horizontally across the lower, or base, portion 42 of the chamber 35 to separate the fibres 43 from the paper stock 29 while permitting the liquid filtrate 44 of the stock to rise into the upper portion 45 of filtration chamber 35.

Preferably the standpipe 34 is fixed on the outlet end of a shutoff valve 46 of the ball type, the valve 46 being fixed to a main paper stock line 23. Standpipe 34 is pivotable on the hinge 47 at one side thereof and clamped by the releasable clamp 48 at the other side thereof. Valve 46 is normally open and forms a means whereby the chamber 35 is directly connected to the interior of the stock line 23, but since the standpipe is closed at the upper end 36, the stock system remains closed rather than open and may be under any conventional stock pressure. When it is desired to replace a screen 41 with a screen of another mesh size, the valve 46 is closed, the clamp 48 released, the standpipe pivoted away from the valve and the ring 39 replaced. The standpipe is then again clamped to the valve and the valve opened.

Automatic means 50 is provided for alternately decreasing air pressure within the upper portion 45 of chamber 35 and then increasing air pressure within the upper portion 45 of chamber 35. The air exhaust means 51, for decreasing air pressure includes the air conduit 52 connected to the upper portion 45 of chamber 35 and leading to a conduit 53 connected to the atmosphere, to a suitable suction pump of any well known type or to mill suction, all indicated generally at 54. The air pressure means 55, for increasing air pressure includes the air conduit 52 connected to the upper portion 45 of the chamber 35 and leading to a conduit 56 connected to the mill air pressure supply or to an air pump and pressure tank of any well known type indicated generally at 57. Suitable manually operable valve may be interposed in air conduits 53 and 56 for manually actuating the freeness tester 33 but preferably the actuation is automatic by means of a cycle timer 58, having a pre-set air pressure and exhaust and including timing means and valves for actuating the tester periodically at predetermined time intervals.

In the embodiment illustrated herein, the freeness is determined by the amount of liquid that rises in the tube, for a given period of time, for a specified pressure differential. This same result could be obtained by measuring the time required for a given level to rise in the tube at a specified pressure differential.

The chamber 35 is normally filled with air under the specified pressure of the positive diiferential pressure cycle to force the paper stock downwardly until the entire vertical space from the closed end 36 of the standpipe to the level of the main stock line 23 at 61 is clear of paper stock (FIG. 2). At preselected time intervals, cycle timer 58 actuates the air exhaust means 51 to withdraw air from the upper portion 45 of chamber 35 at the specified pressure of the negative differential pressure cycle thereby permitting the paper stock 29 to rise in a column in valve 46 and into the standpipe 34. The fibres 43 in the stock are screened out by screen 41 while the liquid continues to rise in a liquid column into chamber 4-5 (FIG. 3). Since the system employs constant time, the column of liquid attains its maximum level at the end of the negative differential pressure cycle. Suitable level indicia 63 on the standpipe 34, representing the desirable and normal freeness of the stock, may then be compared visually, through the transparent standpipe with the actual level so attained to notify the operator of any variations from normal freeness. In addition, preferably, other means are provided for such visual comparison in the form of a liquid level sensitive device 64, of any well known type, for sensing each successive maximum liquid level attained in the chamber 35. The liquid level sensing device 64 is operably connected to a liquid level recorder 65, also of a well known type, for permanently recording the results of each freeness test as well as comparing the same visually with a norm.

As shown in FIG. 5, when the maximum liquid level has been attained in standpipe 34 and has been sensed and recorded, the cycle timer 58 automatically de-actuates exhaust means 51 and actuates air pressure means 55 for increasing air pressure in the upper portion 45 of chamber 35. As air pressure increases in standpipe 34 the liquid column above screen 41 is forced downwardly through the screen to clear the screen of them at 62, and the fibres 43, and back, or reverse flows all of the stock down to level 61 and back into the stock line 23. The tester is thus ready for the next testing cycle.

As best shown in FIG. 6, a pneumatic recorder controller 66, of a well known type, may be substituted for the recorder 65, and connected to the air lines 27 and 28 of the refiners for regulating the refiners to compensate for variations from normal freeness sensed by the recorder-controller. The air supply 57 may be at 100 p.s.i. and reduced in pressure by regulators of well known type to supply an output of 5 to 15 psi. at the controller 66. Similarly the air pressure introduced into chamber 35 may be varied by suitable means to conform to the pressure needed to clear the standpipe 34 and valve 46 of stock.

The screens 41 are preferably formed of an upper portion of fine mesh screen wire 67 supported on a lower portion of coarse mesh screen wire 68 but the screens 41 may consist of a single perforated metal sheet.

It will be understood that the air pressure means 55 is arranged to establish a uniform positive pneumatic pressure differential in chamber 35 and the air exhaust means 51 is arranged to establish a uniform negative pneumatic pressure differential in chamber 35 for uniformity of test results but that high pressure, low pressure, time on and time off can all be adjusted as desired in cycle timer 58.

Suitable recorder, or recorder controller, equipment for sensing liquid level, recording the same and translating the same into proportional air pressure to control the action of a refiner is commercially available from Taylor Instruments Company, Rochester, New York, the Foxboro Company, Foxboro, Massachusetts or many other companies.

As shown in FIG. 6 the apparatus 32 may also include a pair of spaced electric probes 70 and 71 each terminating at a different height in chamber 35 and each connected in an electric circuit 72 which includes a source of current 73 and an electric indicating panel 74 as another means for visually indicating the results of the freeness tests.

The freeness tester, or detector, is similar to tester 33 except that the screen 81 is mounted between a pair of fiat, apertured plates 82 and 83, the plates having a handle 84 and being clamped in a split 86 in the base 35 of the tester. The base 85 is connected to the valve 46 by a bolt such as 87 on each opposite side of the split 86, each bolt extending across the split 86 and a pair of coil springs, such as 88, being associated with each bolt. Normally the device is sealed against leakage by the 0 rings 91 and 92 with the bolts 87 tightened and the springs compressed. To slidably remove the plates 82 and 83 and screen 81, the bolts are loosened to permit the springs to lift detector 80, unclamp the plates and free the plates for slidable withdrawal.

In the device of FIG. 6, the blow-down step occurs when the main cycle timer 58 opens the valve 101, by means of solenoid 102, the vent valve 103 being normally closed and the valve 104 being normally closed. The sample taking step occurs when main cycle timer 58 closes valve 101 and opens vent valve 103, by means of solenoids 102 and 105, and maintains this condition for a suitable time interval. The measurement step occurs at the end of the selected time interval when cycle timer 58 opens valve 104, by means of solenoid 106, thereby permitting recorder controller 66 to receive a signal of liquid height from the water level transmitter 164. In this instance the signal is pneumatic from the air line 107. The liquid level attained in each such cycle is recorded and the cycle may be repeated at such time intervals as may be desired. Manually operable valves 110, 111 and 112 may also be provided corresponding to the solenoid operated valves 102, 103 and 104.

The recorder controller 66 automatically compares the results of each successive test with a predetermined normal freeness and if an abnormal variation from the normal is detected, the recorder controller 66 automatically adjusts the refiners to compensate therefor.

I claim:

1. Apparatus for testing the freeness of paper stock flowing in a closed paper stock line, said apparatus comprising a vertical standpipe of predetermined height and diameter forming a closed, vertical chamber with an open lower end; means directly connecting the open lower end of said chamber to the interior of said line for incorporating said chamber into said closed paper stock line; a horizontal screen mounted across the base portion of said standpipe chamber for separating the fibres from the liquid of said paper stock; air exhaust means connected to the upper portion of said closed chamber for withdrawing air therefrom to permit liquid from said paper stock line to rise thereinto while said fibres form a mat on said screen; air pressure means connected to the upper portion of said closed chamber for introducing air thereinto to clear said chamber of said liquid and to clear said screen of said matted fibres; automatic cycling means for actuating said air pressure means and said air exhaust means at preselected time intervals, and means, associated with said standpipe, visually comparing the maximum level attained therein by said liquid, during each cycle, with a predetermined liquid level indicia for indicating the relative freeness of said paper stock.

2. Apparatus for periodically testing the freeness of paper stock flowing in a closed paper stock line, said apparatus comprising a standpipe having a closed, vertical chamber with an open lower end; means directly connecting the open lower end of said chamber to the interior of said line for incorporating said chamber into said closed paper stock line; a horizontal screen extending across the lower portion of said chamber for separating the fibres from the liquid in said stock; air exhaust means, connected to the upper portion of said chamber, for withdrawing air therefrom and permitting liquid from said paper stock to flow upwardly in said chamber while said fibres form a mat on said screen; air pressure means connected to the upper portion of said chamber for back flowing said liquid downwardly into said line and for clearing said screen of said fibres; means associated with said apparatus for automatically actuating said air exhaust means and said air pressure means at preselected 6 time intervals and means responsive to the maximum level attained by said liquid at each said interval for successively recording the same.

3. Apparatus as specified in claim 2 wherein said horizontal screen includes a lower portion of coarse meshed wire and an upper portion of fine meshed wire.

4. Apparatus as specified in claim 2 wherein said means connecting said chamber to said line includes a shutoii valve interposed between said standpipe and said paper stock line and said standpipe is hingedly clamped on said valve.

5. Apparatus as specified in claim 2 wherein said standpipe is an elongated, transparent tube having a closed upper end and having said screen supported in a ring removably mounted across the lower end of said tube.

6. Apparatus as specified in claim 2 wherein said automatic actuation means is a cycle timer, said air pressure means includes mechanism for establishing a predetermined, uniform positive pneumatic pressure differential in said chamber and said air exhaust means includes mechanism for establishing a predetermined, uniform, negative pneumatic pressure differential in said chamber.

'7. Apparatus for maintaining the uniformity of paper stock freeness in a closed paper stock system including stock refiners having automatic controls, said apparatus comprising a standpipe mounted on the main stock line supplied by said refiners, said standpipe having a closed vertical chamber with a lower end opening into the interior of said stock line to form a part of said closed system, a horizontal screen extending across the lower portion of said chamber for separating fibres from the liquid of said paper stock; air exhaust means connecting with the upper portion of said chamber for establishing a negative pneumatic pressure differential in said chamber, air pressure means connected with the upper portion of said chamber for establishing a positive pneumatic pressure difierential in said chamber; automatic cycling means for actuating said air pressure means and said air exhaust means at preselected time intervals and means, responsive to the maximum level of liquid attained in said chamber during each cycle, for actuating the controls of said refiners whereby variations in stock characteristics, determinable by freeness tests, are corrected in advance of the paper making machine.

8. Apparatus as specified in claim 7 wherein said means for actuating the controls of said refiners includes a pneumatic recorder for permanently indicating relative freeness of the stock in said paper stock line.

9. Apparatus as specified in claim 7 wherein said standpipe is a transparent plastic tube for revealing the height of a column of liquid therein, a shutofi valve is interposed between said standpipe chamber and said stock line and said standpipe is detachably connected to said valve for permitting removal of said screen.

10. Apparatus as specified in claim 7 plus a plurality of spaced electric probes within said chamber, an electric indicating panel having relative freeness indicia thereon and an electric circuit including said probes, said indicia and a source of electricity for visually notifying an oper ator of the freeness of said stock in each said cycle.

11. Apparatus for periodic testing of freeness of paper stock flowing through a closed paper stock system, said apparatus comprising a vertical, closed standpipe mounted on a main stock line pipe of said system, said standpipe having a filtration chamber and an open lower end; means directing connecting the open lower end of said chamber to the interior of a line in said system for including said chamber in said closed paper stock system; a horizontal screen mounted across said chamber within the lower portion of said standpipe for separating fibres from the liquid of said paper stock; automatic cycling means operably connected to said standpipe for alternately decreasing air pressure within the upper portion of said chamber until liquid has attained a stable level therein and then increasing air pressure within said upper portion until said standpipe is clear of paper stock; liquid level sensing means operably connected to said standpipe and recorder means, responsive to said liquid level means, for permanently indicating each successive maximum liquid level attained in said standpipe during each cycle.

12. Apparatus as specified in claim 11 plus pneumatic controller means, actuated by abnormal variations in liquid level sensed by said liquid level means, during each cycle, for effecting compensation therefor Within said paper stock system and in advance of said standpipe.

13. The method of periodically determining the freeness of paper pulp flowing through a closed paper stock system which comprises flowing a stream of said stock upwardly into a vertical column while screening out the fibres in said stock at the base of said column, for a predetermined period, while said stock is within said system; then measuring the maximum height of the resulting liquid column while said liquid is still within said system and then reverse flowing the liquid in said vertical column back into the stock flowing in said closed paper stock system.

14. Apparatus as specified in claim 2 wherein said means connecting said chamber into said line includes a split, said screen is mounted between a pair of plates sealed and clamped in said split and said means includes bolts extending across said split for unclamping said plates to slidably remove said screen.

15. In a freeness tester, a filtration chamber having an open lower end and a closed upper end; a mat-forming screen extending across said chamber proximate said lower end; means mounting said tester on a stock line of a closed paper stock system with the open lower end of said chamber directly connected to the interior of said stock line as part of said closed system; air conduit means in said tester proximate the upper end of said chamber, air pressure means, connected to said air conduit means, said air pressure means being adapted to alternately create positive and negative air pressure in said chamber to admit a column of filtrate thereinto from said system and to then discharge said filtrate back into said system and automatic cycling means for actuating said air pressure means at preselected time intervals for predetermined time periods.

16. The method of maintaining uniformity of paper characteristics in a paper making system by means of a closed standpipe which comprises the steps of periodically, automatically testing the freeness of the paper stock in a closed paper stock line, in advance of the paper making machine but in rear of the stock refiners, said step including the steps of withdrawing a filtrate into said standpipe from said line, through a mat of the fibrous material in said stock, determining the filtrate level attained in said standpipe within a predetermined period of time, and then discharging said filtrate through said mat back into said line; automatically comparing the level of each successive test with a predetermined level indicative of normal freeness and automatically adjusting the refining effect of said refiners to compensate for any variations from normal freeness indicated by said tests.

17. In a device for controlling the freeness of paper stock containing suspended fibrous material;

a closed stock supply system including a stock refiner having a pair of parts rotatably movable with respect to each other;

means for driving one of said parts with respect to the other part;

means for changing the refining effect of said refiner;

enclosed standpipe means having a filtrate chamber and an open lower end directly connected with the interior of said system, a mat forming screen afi'ixed to the standpipe across the lower end thereof, means connected to the standpipe for periodically evacuating said chamber for a predetermined period of time to draw stock through said screen, measuring means for ascertaining the filtrate level attained in said standpipe means during said predetermined period of time, and a source of pressure for discharging said filtrate from said chamber back into said closed stock line through said screen; and

means for operatively connecting said measuring means with said means for changing the refining effect of the refiner so as to increase the refining effect of the refiner when the freeness of the stock within said system increases and to decrease the refining effect when the freeness of the stock within said system decreases.

References Cited by the Examiner UNITED STATES PATENTS 1,876,563 9/32 Buchner l62-l98 1,945,988 2/34 Witham 7363 X 2,210,027 8/40 Cram 7363 X 2,711,750 6/55 Norcross 13792 2,734,378 2/56 Meyers 73-63 3,058,672 10/62 Zabel 24137 RICHARD C. QUEISSER, Primary Examiner.

C. A. CUTTING, ROBERT L. EVANS, JOSEPH P.

STRIZA'K, Examiners. 

1. APPARATUS FOR TESTING THE FREENESS OF PAPER STOCK FLOWING IN A CLOSED PAPER STOCK LINE, SAID APPARATUS COMPRISING A VERTICAL STANDPIPE OF PREDETERMINED HEIGHT AND DIAMETER FORMING A CLOSED, VERTICAL CHAMBER WITH AN OPEN LOWER END; MEANS DIRECTLY CONNECTING THE OPEN LOWER END OF SAID CHAMBER TO THE INTERIOR OF SAID LINE FOR INCORPORATING SAID CHAMBER INTO SAID CLOSED PAPER STOCK LINE; A HORIZONTAL SCREEN MOUNTED ACROSS THE BASE PORTION OF SAID STANDPIPE CHAMBER FOR SEPARATING THE FIBRES FROM THE LIQUID OF SAID PAPER STOCK; AIR EXHAUST MEANS CONNECTED TO THE UPPER PORTION OF SAID CLOSED CHAMBER FOR WITHDRAWING AIR THEREFROM TO PERMIT LIQUID FROM SAID PAPER STOCK LINE TO RISE THEREINTO WHILE SAID FIBRES FORM A MAT ON SAID SCREEN; AIR PRESSURE MEANS CONNECTED TO THE UPPER PORTION OF SAID CLOSED CHAMBER FOR INTRODUCING AIR THEREINTO TO CLEAR SAID CHAMBER OF SAID LIQUID AND TO CLEAR SAID SCREEN OF SAID MATTED FIBRES; AUTOMATIC CYCLING MEANS FOR ACTUATING SAID AIR PRESSURE MEANS AND SAID AIR EXHAUST MEANS AT PRESELECTED TIME INTERVALS, AND MEANS, ASSOCIATED WITH SAID STANDPIPE, VISUALLY COMPRISING THE MAXIMUM LEVEL ATTAINED THEREIN BY SAID LIQUID, DURING EACH CYCLE, WITH A PREDETERMINED LIQUID LEVEL INDICIA FOR INDICATING THE RELATIVE FREENESS OF SAID PAPER STOCK. 